The present invention relates to a nitrogen-containing flame retarding epoxy resin and their composition comprising the nitrogen-containing flame retarding epoxy resin.
Under the consideration of economics and productivity, an encapsulating material for currently semiconductor devices is an epoxy-based resin composition. To insure the use safety. electronic parts for the semiconductor are required to meet a flame retarding specification regulated by the UL. The approach to attain the flame retarding specification is addition of halogen-containing epoxy resin and diantimony trioxide as a flame retarding assistant into epoxy resin compositions for encapsulating electronic parts. However it is known that such flame retarding assistants are harmful to human and animal. For example. Diantimony trioxide has been classified a cancerous material while an epoxy resin containing halogen such as bromine will produce corrosive bromine free radical and hydrogen bromide during burning. Also, an aryl compound containing high content bromine will produce toxic brominated furanes and brominated dioxins compounds. Such toxic material have adverse effects to human, animal and environment. Thus, it is eagerly required to semiconductor manufacture for developing a novel epoxy resin without halogen neither diantimony trioxide to resolve the problems associated with the use of halogen-containing epoxy resin and diantimony trioxide.
For flame retarding resins, a nitrogen-containing compound is widely used as a new generation flame retarding agent. Among others, examples of commonly used flame retarding agents include non-reactive type nitrogen-containing compounds such as melamine, and triazine-containing cyanate, and non-reactive phosphorus-containing compounds such as red phosphorus, triphenyl phosphate (TPP), tricresyl phosphate (TCP), and poly(ammonium phosphate), and non-reactive nitrogen-containing flame retarding agent such as melamine dimer and trimer. To attain desired flame retarding effect is required to incorporating such non-reactive flame retarding agent in a large amount to epoxy resin composition formulations, which will cause the lowing of relative amount of the epoxy resin and the curing agent contained in the formulation so that the performances of the epoxy formulation will decrease.
Recently, under the considerations of environmental protection and safety, a reactive type resin flame retarding agent is used to substitute for currently used flame retarding agent. Since reactive nitrogen-containing flame retarding resin can react with other components and has better heat stability, it is widely used to substitute for halogen-containing resin. For example, Japan Unexamined Patent Publication No. 2000-297284 discloses a reactive type nitrogen-containing flame retarding agent which is a product from reacting a triazine compound and formaldehyde. Japan Examined Patent Publication No. Hei 6-31276 discloses a phosphorous-containing organic cyclic compound as a flame retarding agent. In addition, EP 0877040A1 discloses a novolac phenolic resin composition containing triazine ring possessing a flame retarding property. Such reactive type nitrogen-containing compounds have widely been used as a flame retarding agent in resin composition to be required a flame retarding property for electronic parts. Currently, the development of such reactive type nitrogen-containing flame retarding resin is mainly novolac-based resin, but for semiconductor encapsulating, such a novolac-based resin composition can not improve a flame retarding property of the resin composition due to its low addition proportion.
To overcome the disadvantages associated with the current semiconductor encapsulating technique, the present inventors have investigated on epoxy resin and then developed a modified nitrogen-containing epoxy resin. Thus the present invention is completed.
The nitrogen-containing epoxy resin of the present invention has excellent flame retardant effect and heat resistance, it is therefore useful as an encapsulating material or semiconductor and imparts the encapsulated article with excellent flame retardant effect and heat resistance. Further, the nitrogen-containing epoxy resin of the present invention is also useful as a flame retarding agent or stabilizer for resin other than epoxy resin, such as thermoset and thermoplastic resin and is useful for producing various electronic products.
The present invention relates to a nitrogen-containing epoxy resin of the following formula: 
wherein R""s are the same or different and each represents a hydrogen atom or xe2x80x94R13xe2x80x94C6-10 aryl-(OR14)p, and the aryl group is optionally substituted with C1-6 alkyl group, in which R13 represents a C1-6 alkylene group or a phenylene xe2x80x94CH2xe2x80x94 group optionally substituted with a hydroxy group, R14 represents a glycidyl group, and p is an integer of 1 or 2, provided that at least one R group is not a hydrogen atom; R1 represents a phenyl group or xe2x80x94N(R)2 group in which R is defined as above;
which is produced from reacting melamine derivatives sequential with aldehydes, phenolic compound and epihalohydrin.
The present invention also relates to a flame retarding epoxy resin composition comprising the nitrogen-containing epoxy resin of the present invention.
The present invention further relates to a flame retarding epoxy resin composition comprising the nitrogen-containing epoxy resin of the present invention and a phosphorous-containing, flame retarding agent: 
wherein R1 represents xe2x80x94Oxe2x80x94, xe2x80x94NiH2xe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, CH2CON less than ; Ar represents a phenylene group, a biphenylene group, a bisphenol divalent group, a polyphenol divalent group, a divalent group selected from the following formulae: 
wherein R2 represents a hydrogen atom, a C1-6 alkyl or C1-6 aryl;
R3 represents xe2x80x94OH, xe2x80x94NH2, xe2x80x94SH, xe2x80x94COOH, xe2x80x94SO3H, xe2x80x94CHO, xe2x80x94NHCOCH3;
R4 represents xe2x80x94CH2xe2x80x94, xe2x80x94(CH3)3Cxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94Oxe2x80x94;
m represents an integer of 0 to 2, and n represents an integer of 1 to 20.
Furthermore, the present invention also relates to the use of the present nitrogen-containing epoxy resin as a flame retarding agent or stabilizer for resin material other than epoxy resin which is in turn useful for producing various electronic products.
The term xe2x80x9cC1-6 alkyl groupxe2x80x9d used herein means a liner or branched alkyl group having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl and isohexyl and the like. The term xe2x80x9cC1-6 alkylene groupxe2x80x9d used herein means a residue obtained by subtracting two hydrogens atom from a linear or branched alkane having 1 to 6 carbon atoms.
The term xe2x80x9cC1-6 aryl groupxe2x80x9d used herein means an aryl group having from 6 to 12 carbon atoms, such as phenyl group, naphthyl group, and biphenyl group and the like.
The term xe2x80x9carylene groupxe2x80x9d used herein means a residue obtained by subtracting two hydrogens atom from an aromatic hydrocarbon.
The term xe2x80x9cC1-6 aryl groupxe2x80x9d used herein means an aryl group having from 6 to 12 carbon atoms, such as phenyl group, naphthyl group, and the like.
The flame retarding nitrogen-containing epoxy resin according to the present invention is prepared from reacting melamine derivatives sequential with aldehydes of formula R12COH, functional-containing benzene compound and epihalohydrin. Thus, the present invention also relates to a process for producing a flame retarding nitrogen-containing epoxy resin, the process comprises:
(a) reacting melamine derivatives of following formula (2): 
xe2x80x83(in which R5 represents xe2x80x94NH, or a phenyl group), with aldehydes of formula R12 COH (in which R12 represents C1-6 alkyl group or unsubstituted or hydroxy-substituted phenyl group) in a suitable reaction solvent at a temperature of from 40 to 150xc2x0 C., preferably at a temperature of from 60 to 100xc2x0 C., to give a hydroxy-containing triazine derivative containing a functional group of the formula xe2x80x94NHCR12HOH; and
(b) dehydrating the resultant hydroxy-containing triazine derivative with phenolic compound in the presence of acidic catalyst at a temperature of from 50 to 200xc2x0 C., preferably at a temperature of from 80 to 150xc2x0 C., to give hydroxy- and aryl-containing triazine derivative;
(c) epoxizating the resultant hydroxy- and aryl-containing triazine derivative with epihalohydrin in the presence of a base to give the flame retarding nitrogen-containing epoxy resin of the present invention.
In the step (a), the mole ratio of melamine derivatives of formula (2) to aldehydes of formula R12COH is from 0.1 to 1.5, preferably from 0.3 to 1.0.
Examples of the aldehydes suitable in the present invention include formaldehyde, acetaldehyde, propionaldehyde, butylaldehyde, pentaldehyde, benzaldehyde, 2-hydroxybenzaldehyde, and 4-hydroxybenzaldehyde, and the like.
Examples of the solvents suitable in the step (a) include alcohols and aromatic hydrocarbon solvents including, but not limited to, methanol, ethanol, propanol, isopropanol, butanol, t-butanol, methoxyethanol, ethoxyethanol, butoxyethanol, methoxyisopropanol, ethoxyisopropanol, butoxyisopropanol, and the like; and benzene, toluene, and xylene, and the like.
In the step (b), the mole ratio of the resultant hydroxy-containing triazine derivative to the phenolic compound is from 0.02 to 0.5.
Examples of the phenolic compound suitable in the step (b) include, but not limited to, phenol, o-hydroxycresol, m-hydroxycresol, p-hydroxycresol, o-cresol, m-cresol, p-cresol, o-isopropylphenol, m-isopropylphenol, p-isopropylphenol, o-t-butylphenol, m-t-butylphenol, p-t-butylphenol, 2-methyl-4-t-butylphenol, 2-methyl-6-t-butylphenol, 3-methyl-6-t-butylphenol, bisphenol, bisphenol-A, bisphenol-F, bisphenol-S, naphthol, benzoic acid, 2-hydroxybenzoic acid, 4-hydroxybenzoic acid, terephthalic acid, and the like. Among others, phenol, o-hydroxycresol, m-hydroxycresol, o-cresol, m-cresol, p-cresol, o-t-butylphenol, m-t-butylphenol, p-t-butylphenol, 2-methyl-4-t-butylphenol, 2-methyl-6-t-butylphenol, 3-methyl-6-t-butylphenol, bisphenol, bisphenol-A, bisphenol-F, bisphenol-S, naphthol, benzoic acid, 2-hydroxybenzoic acid, and 4-hydroxybenzoic acid, and the like.
Also, the reaction between the hydroxy-containing triazine derivative with the phenolic compound occurs at the para-position or meta-position relative to the hydroxy group of the phenolic compound.
Examples of the acidic catalyst for the dehydrating reaction in the step (b) include, but not limited to, oxalic acid, hydrochloric acid, sulfuric acid, sulfurous acid, nitric acid, nitrous acid, chloric acid, perchloric acid, hypochloric acid, phosphoric acid, phosphorous acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, dimethyl sulfate, diethyl sulfate, and the like. Among others, oxalic acid, hydrochloric acid, sulfuric acid, benzenesulfonic acid, p-toluenesulfonic acid, dimethyl sulfate, diethyl sulfate are preferable. The amount of the acidic catalyst is from 0.0001 to 0.001 mole per mole of the phenolic compound.
In the step (c), the mole ratio of the hydroxy- and aryl-containing triazine to epihalohydrin is from 0.02 to 0.2.
Examples of epihalohydrin used in the step (c) include epihalohydrin, epibromohydrin, and the like. Examples of the base suitable in the step (c) include sodium hydroxide, and the like. The mole ratio of the base to the epihalohydrin is from about 0.01 to 1.0.
The flame retarding nitrogen-containing epoxy resin of the present invention has a high nitrogen content thus possesses excellent flame retarding effect and heat resistance, it therefore can be used as an epoxy resin for producing semiconductor encapsulating material. It can also be incorporated into other thermoset and thermoplastic resin material to produce various electronic products.
Accordingly, the present invention also relates to a use of the flame retarding nitrogen-containing epoxy resin of the present invention as a flame retarding agent in either thermoset or thermoplastic resin.
Examples of the thermoset resin in which the flame retarding nitrogen-containing epoxy resin of the present invention is suitable include, such as, epoxy resin and novolac resin, and the like. Examples of the thermoplastic resin in which the flame retarding nitrogen-containing epoxy resin of the present invention is suitable include, such as, polystyrene, polypropylene, polyterephthalate, polycarbonate, polystyrene, styrene-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyamide, polysulfone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and the like.
The present invention further relates to a flame retarding epoxy resin composition, which comprises the flame retarding nitrogen-containing epoxy resin of the present invention, a curing agent containing reactive hydrogen capable to react with an epoxy group, and a curing promoter.
The curing agent containing reactive hydrogen capable to react with an epoxy group used in the flame retarding epoxy resin composition, hereinafter referred to xe2x80x9cthe curing agentxe2x80x9d, can be various halogen-free curing agent, and includes bisphenol resin, polyhydroxy phenol resin, phenolic resin, and anhydride, and the like.
Examples of the bisphenol resin include compound of the formula HOxe2x80x94Phxe2x80x94Xxe2x80x94Phxe2x80x94OH (wherein Ph represents a phenylene group, Xxe2x95x90 a bond, xe2x80x94CH2xe2x80x94C(CH3)2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94 or xe2x80x94SO2xe2x80x94). Embodiments of the bisphenol resin include, but not limited to, tetramethylbisphenol AD, tetramethylbisphenol S, 4,4xe2x80x2-biphenol, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenol, or 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-4,4xe2x80x2-biphenol, and the like.
Examples of the polyhydroxy phenol resin include, but not limited to, tris(4-hydroxyphenyl)methane, tris(4-hydroxyphenyl)ethane, tris(4-hydroxyphenyl)propane, tris(4-hydroxyphenyl)butane, tris(3-methyl-4-hydroxyphenyl)methane, tris(3,5-dimethyl-4-hydroxyphenyl)methane, tetrakis(4-hydroxyphenyl)methane, tetrakis(3,5-dimethyl-4-hydroxyphenyl)methane, and the like.
Examples of the phenolic resin include phenol-formaldehyde condensate cresol-phenolic condensate, bisphenol A-phenolic condensate and dicyclopentadiene-phenolic condensate, and the like.
Examples of the anhydrides include, such as 3,3xe2x80x2,4,4xe2x80x2-benzophenonetetracarboxylic anhydride (BTDA), trimetallitic acid trianhydride (BTDA) and pyromellitic acid dianhydride, and the like.
The curing agent used in the flame retarding epoxy resin composition of the present invention can be a nitrogen- and phosphorus-containing curing agent of the following formula: 
wherein R7 represents a group of formula xe2x80x94NHR6, C1-6 alkyl group or C1-6 aryl group; R6 represents a hydrogen atom, a group of the formula xe2x80x94(CH2xe2x80x94R8)rH, or a group of following formula (5), provided that at least one R6 is not a hydrogen atom, in which R8 represents a phenylene group, a naphthalene group, or a group of formula (4): 
wherein r represents 0(zero) or an integral of from 1 to 20; A represents xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94 or a group of the following formula: 
in which R9 and R10 independently represent a hydrogen atom, a C1-10 alkyl group, or a C1-6 aryl group; Y represents xe2x80x94OH, xe2x80x94NH2, or xe2x80x94COOH; a represents 0(zero) or an integral of from 1 to 2; x represents 0(zero) or an integral of from 1 to 3; 
in which R11 is defined as the definition for R8 and r is defined as above.
The C6-10 aryl group represented by R7 and R10 can further be substituted with one or more substitutents selected from the group consisting of a hydroxy group, an amino group, a carboxyl group, a C1-6 alkyl group, and a combination thereof.
The term xe2x80x9caryl groupxe2x80x9d used herein includes phenyl group and naphthyl group.
Examples of the curing promoter used in the flame retarding epoxy resin composition of the present invention include tertiary amine, tertiary phosphine, quaternary ammonium salt, phosphornium salt, boron trifluoride complex, lithium compound or imidazole compound, or a combination thereof.
Examples of the tertiary amine include trimethylamine, triethylamine, diusopropyl ethylamine, dimethyl ethanolamine, diethylaniline, tris(N,N-dimethylaminomethyl)phenol, or N,N-dimethylaminomethyl, and the like.
Examples of the tertiary phosphine include triphenylphosphine.
Examples of the quaternary ammonium salt include tetramethylammonium chloride, tetramethylammonium bromide, triethylbenzylammonium chloride, triethylbenzylammonium bromide, or triethylbenzylammonium iodide, and the like.
Examples of the phosphornium salt include tetrabutylphosphomium chloride, tetrabutylphosphornium bromide, tetrabutylphosphornium iodide, tetrabutylphosphate acetate complex, tetraphenylphosphornium chloride tetraphenylphosphornium bromide, tetraphenylphosphornium iodide, ethyltriphenylphosphornium chloride, ethyltriphenylphosphornium bromide, ethyltriphenylphosphornium iodide, ethyltriphenylphosphate acetate complex, ethyltriphenylphosphate phosphate complex, propyltriphenylphosphornium chloride, propyltriphenylphosphornium bromide, propyltriphenylphosphornium iodide, butyltriphenylphosphornium chloride, butyltriphenylphosphornium bromide, and butyltriphenylphosphornium iodide, and the like.
Examples of the imidazole include, such as, 2-methylimidazole, 2-phenylimidazole, or 2-ethyl-4-methylimidazole, and the like.
These curing promoter can be used along or in a combination thereof.
The flame retarding epoxy resin composition of the present invention, in addition to the flame retarding nitrogen-containing epoxy resin of the present invention, can also comprise other conventional epoxy resin. Examples of the conventional resin include, such as, bisphenol glycidyl ether, bis(diphenol) glycidyl ether, resorcinol glycidyl ether, glycidyl ether of a nitrogen-containing ring, glycidyl ether of dihydroxynaphthalene, phenolic polyglycidyl ether, and polyhydroxy phenol polyglycidyl ether, and the like.
In the flame retarding epoxy resin composition of the present invention, the amount of the curing agent depends on the epoxy equivalent of the used epoxy resin and the active hydrogen equivalent of the curing agent. Generally, the ratio of the epoxy equivalent of the epoxy resin to the active hydrogen equivalent of the curing agent is from 1:0.5 to 1:1.5, preferably from 1:0.6 to 1:1.4, more preferably from 1:0.7 to 1:1.3.
When the flame retarding epoxy resin composition of the present invention contains both the flame retarding nitrogen-containing epoxy resin of the present invention and conventional epoxy resin, the amount of the conventional epoxy resin is from 1 to 95% by weight, preferably from 30 to 90% by weight, more preferably from 35 to 88% by weight, relative to the total weight of the epoxy resin contained in the flame retarding epoxy resin composition of the present invention. In the other hand, if the amount of the flame retarding nitrogen-containing epoxy resin of the present invention is less than 5% by weight, the resultant flame retarding property and heat resistance are insufficient.
In the flame retarding epoxy resin composition of the present invention, the amount of the curing promoter is from 0.01 to 5% by weight, preferably from 0.05 to 3% by weight, relative to the total weight of the flame retarding epoxy resin composition of the present invention. If the amount of the curing promoter is more than 5% by weight, although it causes shorten reaction time, it easily produces byproducts, which adversely affects the electronic property, moisture resistance, water absorbability in the final use. If the amount is less than 0.01% by weight, the reaction rate is too low so that the production is inefficient.
The amount of the curing promoter also depends on a gelling time and viscosity of the flame retarding epoxy resin composition of the present invention. Generally, the curing promoter is added in an amount that controls the gelling time of the flame retarding epoxy resin composition of the present invention in the range of 30 to 500 sec/171xc2x0 C., and the viscosity of the flame retarding epoxy resin composition of the present invention in the range of 20 to 500 cps/25xc2x0 C.
The flame retarding epoxy resin composition of the present invention further comprises other additives, for example, such as inorganic filler, coupling agent, pigment (e.g. carbon black and ferrous oxide), molding release agent and low stress additives.
Examples of the inorganic filler suitably used in the flame retarding epoxy resin composition of the present invention include sphere type and cornered type molten silica, crystalline silica, and the like, and quartz glass powder, talc powder, alumina powder, zinc borate, aluminum hydroxide, magnesium hydroxide, calcium carbonate, aluminum nitride, and the like. These filler can be used alone or in a combination thereof. With the cornered type molten silica, crystalline silica, and a mixture of the cornered type molten silica and crystalline silica are preferred.
An average particle size of these inorganic filler is preferably from 1 to 30 micron. If the average particle size is less than 1 micron, it will cause the increasing viscosity and decreasing flowability of the resin composition. If the average particle size is more than 30 micron, it will cause uneven dispersion of the resin and of the filler in the epoxy resin composition, which will in turn cause resin overflowing during encapsulating application and affect physical property of the cured article. Additionally, the maximum particle size is preferably less than 150 micron to avoid causing a narrow casting channel or poor filling of voids.
The amount of the inorganic filler is from 60 to 92% by weight, preferably from 65 to 90% by weight based on the total weight of the flame retarding epoxy resin composition of the present invention. If the amount of the inorganic filler is less than 60% by weight, the relative ratio of the epoxy resin in the resin composition will be increased so that an overflowing of the resin easily occurs during encapsulating. If the amount of the inorganic filler is more than 92% by weight, a viscosity of the resin composition will increase and result in the decrease of flowability.
The present invention will further illustrate by reference to the following synthesis examples, working examples, and comparative examples, However, these synthesis examples and working examples are not intended to be limiting of the scope of the present invention.
The epoxy equivalent weight (EEW), the viscosity, and a soften point used herein are determined according to the following methods:
(1) Epoxy Equivalent Weight (EEW): The epoxy equivalent weight (EEW) is determined according to the method of ASTM 1652, the epoxy resin to be tested is dissolved in a mixture solvent of chlorobenzene:chloroform in a weight ratio of 1:1, the resultant mixture is titrated with HBr/galacial acid by using crystalline violet as an indicator.
(2) Viscosity: The viscosity is determined by placing the epoxy resin to be tested in a thermostat maintaining at 25xc2x0 C. for 4 hours and measuring the viscosity by using Brookfield Viscosmeter at 25xc2x0 C.
(3) Soften point: The soften point is determined by applying the epoxy resin to be tested on an O-ring, placing a ball on the applied epoxy resin gradually heating the epoxy resin, and measuring the temperature when the ball falls into the O-ring.
Each ingredients used in these synthesis examples, working examples, and comparative examples are illustrated as follows.
Epoxy resin A: cresol-phenolic condensate having an epoxy equivalent weight of 200 to 220 gram/equivalent and a hydrolyzable chlorine of below 200 ppm, under trade name of CNE 200ELB sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan. R.O.C.
Epoxy resin B: 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-4,4xe2x80x2-biphenol having an epoxy equivalent weight of 195 grain/equivalent, under trade name of YX4000H sold and manufactured by Yuka Shell Epoxy Co. Ltd., Japan.
Epoxy resin C: a diglycidyl ether of tetrabromobisphenol A having an epoxy equivalent weight of 330 to 350 gram/equivalent, under trade name of BEB350 sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan, R.O.C.
Curing agent A: a curing agent having reactive hydrogen of 105 to 110 gram/equivalent, under trade name of PF-5110 sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan, R.O.C.
Curing agent B: a nitrogen- and phosphorus-containing curing agent prepared from the following Synthesis Example 3.
Curing promoter A: triphenylphosphine.
Curing promoter B: 2-methylimidazole (hereinafter referred to 2MI).